1. Field of the Invention
The present invention relates to an articulating headrest for use with chairs, specifically dental chairs, and to a headrest which may be operated with one hand and which exhibits unhindered movement in a forward direction and restricted movement in a backward direction relative to the backrest of the chair to which it is attached.
2. State of the Art
The positioning of a headrest on a medical or dental chair relative to a patient's head has been considered previously. For example, U.S. Pat. No. 4,111,483 (Jaeger), U.S. Pat. No. 4,111,484 (Jaeger) and U.S. Pat. No. 4,128,274 (Schmedemann) are directed primarily to the vertical positioning of a headrest relative to a patient's head. The Schmedemann patent also discloses methods for the horizontal positioning of a headrest.
While vertically and horizontally adjustable headrests generally can increase patient comfort upon proper positioning, such devices are not entirely satisfactory and it is beneficial to the comfort of a patient to provide rotational movement of a headrest relative to the backrest to which it is attached. Rotatively movable headrests are shown in U.S. Pat. No. 3,817,576 (Ciavattoni), U.S. Pat. No. Re. 29,811 (Norris) and U.S. Pat. No. 3,936,091 (Rabinowitz). However, the headrests described therein also have not been entirely satisfactory. The Ciavattoni device, for example, locks the headrest only in discrete positions defined by slots in the headrest which are engaged by the pawl mechanism of the device. The positive locking mechanism is potentially dangerous in the working environment in which the headrest and chair are used. When the dental chair is placed into a reclining position, the headrest can contact various objects in the operating environment such as stools, carts and the like and subject them to damaging forces. Absent a release mechanism on the headrest, the objects so contacted may be damaged irreparably. The Norris device utilizes a cam-actuated locking mechanism having a cam surface which exerts a compressive force on a linking member to reduce the diameter of openings in which pivotable pins normally can rotate, thus preventing their rotation and the rotation of the headrest. Both forward and backward movement of the headrest relative to the backrest is prevented. Accordingly, the Norris devices exemplifies the deficiencies of the Ciavattoni device considered above. While the Rabinowitz device permits rotational movement of the headrest in the forward direction upon subjecting the headrest to forces in that direction, the cam-actuated clutch mechanism is complicated and can lead to high manufacturing costs. Furthermore, the toothed clutch mechanism can lead to premature wear if movement of the headrest is attempted without complete disengagement of the clutch members. Continuous wear can impair the positive locking mechanism and lead to slippage of the clutch members.
Accordingly, it is apparent that there is a need for a simplified articulating headrest, for use with medical and dental chairs and the like, which can be positionally varied over non-discrete positions and which provides a positive locking mechanism to prevent backward rotational movement while permitting unhindered forward rotational movement.